The Pictured Rove Beetle is found along the Pacific Coast of North America, from southern Alaska to Baja California (Wikipedia 2011
). It inhabits west-coast sand beaches where it feeds primarily on beach-hopper amphipods Megalorchestia
spp. The beetle in both instar and adult stages digs temporary burrows above the high-tide mark, emerging on overcast days and at night to prey on crawling or even jumping amphipods. The beetle is largely an ambush predator, is sensitive to vibration, and with its sickle-shaped jaws can quickly subdue, dismember, gut, and eat even relatively large amphipods. The amphipods have no defenses beyond their jumping ability. However, if they land within a few centimeters of a beetle, in the short time it takes them to re-position themselves, they may be attacked. The beetles follow the tides and their prey up and down the beaches apparently using moisture gradients in the sand for orientation. For more on their predatory activities go to A SNAIL'S ODYSSEY
and scroll down to INSECTS.
Note Author: Tom Carefoot, Department of Zoology, University of British Columbia